Many examples of mechanical sweepers are known in which a conveyor is used to convey material from a main broom of the sweeper which engages the ground to a dirt hopper carried on the sweeper. An example of this construction is shown in U.S. Pat. No. 5,054,152 belonging to Hulicsko. Mechanical sweepers with a conveyor pickup mechanism are known to be good for denser materials including sand and the like which commonly require cleaning in the spring after sand is used on roads throughout a winter, however the hoppers have a limited capacity and are accordingly not well suited to collecting large masses of leaves and the like in the fall.
Another variety of street sweeper involves a vacuum sweeper, for example as shown in U.S. Pat. No. 6,948,213 belonging to Kim. In this instance side brooms are used to sweep debris into a central row which is collected by a vacuum head communicating with the dirt hopper by a suitable duct. A blower inlet connects to the hopper to maintain the hopper under vacuum pressure which causes air to be drawn up through the vacuum head and the duct communicating between the vacuum head and the hopper to collect less dense materials such as leaves and the like. Such a sweeper however is not particularly suited for small size, high density materials including sand and rocks and the like. Accordingly users of street sweepers in environments where the climate varies between cold and warm temperatures will often be required to purchase two different configurations of sweepers, one for the collection of leaves in the fall and one for the collection of sand in the spring.